To minimize the risk of accidental ignition.
ground cover in crawl spaces whose exterior walls have less than 25% of their total area above exterior ground level open to the outdoors, that are under 1-
and are used as warm-air
to which Part 9 applies [see
Sentence 184.108.40.206.(1) of Division A
for application of Part 9].
To limit the probability that debris, such as smouldering cigarette butts, will fall through floor registers and lead to the ignition of combustible materials in the crawl space plenum, which could lead to harm to persons.